Alternator



F. w. lDEN Aug. 7, 1945.

ALTERNATOR Filed Sept. 16, 1942 Y s a a 6 6 J 3 L" I 1 1 7 ,7

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INVENTOR. fZam Wan/WIDE ATZ'OEYEY baa-um? m Patented Aug. 7, 1945 2 3 95 UNITED STATES PATENT ormer.

ALTERNATOR Floyd William Iden, Newark, N. J., assignor to Federal Telephone and Radio Corporation, a corporation of Delaware Application September 16, 1942, Serial No. 458,495 9 Claims. (01. 171-252) This invention relates to alternating current with separate stators and rotors, the latter being generators or altemators and in particular to alfixedly mounted on a single shaft. The armature ternators which develop polyphase voltages. coils of the two alternators are so connected that The alternator of my nven i n w s pr mar y the desired 180 hase relation of voltage is-mainde el ped a a power source for emergency r i tained even though the voltage developed inone pparatus to be employed with infl d rubber armature is not in phase with that developed in life boats. Emergency radio apparatus usually th th armature employs the simplest of electrical circuits and the Referring to F'jg 1 t numerals and repmin m f equ pment co sistent w h a desired resent the two stacks of laminations which Power Output and reasonable efllcicncye 1 gether with the permanent magnet z and shaft rectified oscillator circuits adequately meet the 3 comprise the rotor of the t t The 1 mrequirements 1:01- simplicity and efilciency but-they n t and magnet are rigidly held in positions must necessarily employ PWer supply having a on the shaft by clamping them between the flange phase relation of voltages' 4 and the nut 5. The shaft rotates in bearings 6 Q known way of Obtaining Such a Phase and 6 which are mounted in the end shields (not lation of voltages is to produce a single phase shown) or the alternator voltage, and connect it to the primary of a trans- The stator or armature of the alternator com -former thesecondary of which has an intermeof t 1 1 1 diate tap. The two voltages on either side of the sists W0 stac s of 1am Hat ons and Spaced intermediate tap have a 180 phase relation. g gg g mf g z g z i fig 232 ;221 232: However. such method involves the use of Sand spacer Hi. The yoke and spacer serve as a paratus m addmon alternator namely the framefor holding the stator laminations in place transformer, and the weight of and the space and also serve as part, of a magnetic circuit beoccupied by this umt woulq be very undesirable tween the two sets of laminations. The return In accordance with my invention, two voltages ti f t d t to are generated, and then they are divided and remagne c 01 cm or one m or an S a r combination comprises the second rotor and stator. combined in such a manner that regardless of themagnitude and phase relation of the original fi zgg g maignetlc t voltages the resultant combined voltages are m or and S r compr $85 the yo e Wlth 6 l0 stator laminations l rotor laminaequal in magnitude and 180 out of phase. spacer,

It is therefore an object of my invention to dei Hons and permanent magnet vise an alternator which generates two voltages F 2 shows fragmentary section of the rotor which automaticany'mamtam a phase re1a and stator laminations and illustrate the manner non in which the armature coils are connected in the The above mentioned object and further ad- There are twice as many Poles on the vantages of my invention and the manner of obstator as there are poles or! the rotor and due taining them will be explainedin the followi to the permanent magnet all poles of one stator description taken in conjunction with the accomare of one Polarity, ay o t and all D0 o paying drawings in which: the corresponding rotor are of the opposite polar- Fig. 1 is a sectional view taken through the axis 40 W, north- The polarities 0f the p of the of rotation of the alternator. f. second stator and rotorare reversed. As the rotor Fig. 2 is a view of the alternator laminations is re d the magnetic flux between one rotor taken perpendicular to the axigof rotatiqn, pole and one stator pole is increasing while the Fig. 3 is a winding and vectondiagram showi'iig fl x w en the sam rotor pole and an adjacent an undesired phase relation 'of voltages which my Stator D e-i cr in h he en rated invention corrects. E. M. F. is due to a change in flux in the stator Fig. 4 is a schematic wiring diagram showin poles and not to areversal of flux.

. r,-. ,the manner in which the armature coils of the In the illustration of Fig. 2, there are a total alternator are connected so as to give two vo lt-v of 36 poles on the stator and 18' poles on the rotor; ages having al80 phase relation. Therefore, for one revolution of the rotor, 18

Fig. 5 is a vector diagram showing the phase cycles will be generated and if the rotor makes relations of voltages developed in the armature 1800 R. P. M. (or 30 R. P. S.) a 540 cycle per seccoils. v .ond 'altemating voltage will be developed. The

According to one aspect of my invention the magnitude of this voltage (other things being alternator may be considered as two alti'nators equal) will depend on the total number of turns of the armature coils since all coils are connected in series.

What has just been said of one rotor and stator combination is of course also true of the second combination. If the stator poles of each combination are so positioned with respect to their corresponding rotor poles that a maximum voltage is developed in each combination simultaneously, a series connection between the coils of the two stators can be made which will develop a maximum voltage equal to the sum of the separate voltages. A center tap connection between the two stator windings will permit the Obtaining of two voltages having a 180 phase relation.

However, it has been found difllcult to so align the rotor and stator combinations that a maximum voltage is developed in the armature coils simultaneously, with the result that a phase displacement occurs and the desired 180 phase relation no longer exists. It is the object of my invention to correct this condition, which is illustrated by the winding and vector diagram of Fig. 3. In this figure, E1 represents the voltage developed in the armature coils of one stator and E1 represents the voltage developed in the armature coils of the second stator. 4: is the phase displacement from the desired 180 relation.

Referring now to Fig. 4 it will be seen that when the armature coils of each stator are series connected into two separate groups, and a group of one stator is connected in series with a group of the second stator, and the four groups connected in series with a center tap so their voltages are additive, a vector diagram representing these voltages will result as shown in Fig. 5. The total voltages Er. and Er are obviously the sum of the partial voltages and and always maintain a 180 phase relation. For example, in the illustrated case wherein the stators have 36 coils, 18 adjacent coils may be connected in series to form one group while the remaining 18 coils may form the second group. On the other hand, every other coil around the armature may be series connected to form one group while the intermediate coils are series connected to form the second group, Should there be any eccentricity between the rotor and stator whereby the flux gaps between their poles would vary, it would be preferable to connect every other coil in series to form a group. This would tend to equalize the voltages developed in the two groups.

While my invention has been described as it would apply to two rotors and to two stators mounted in a single machine, the same conditions would exist if two separate machines were employed and driven synchronously. The only requirement is that the voltages developed in the armature windings of each machine are so added that a vector diagram of these voltages would give a result as shown in Fig. 5. 'If the two machines were not driven synchronously the two resultant total voltages would still maintain a 180 phase relation but their amplitudeswould vary. In certain instances this variation in amplitude might prove to be a very valuable feature as, for example, in certain types of radio-transmitters, wherein it would be desirable to superimpose a relative low modulation upon the alternating-cub phase opposition.

rent which would normally result it the two machines were synchronously driven. The same result could also be obtained if the two machines were mounted in a single frame with the rotors on a common shaft, as illustrated in Figs. 1 and 2 of this specification, but with each machine having a different number of poles.

Having thus described my invention, 1 claim:

1. An alternator for generating two voltages having a 180 phase relation comprising a frame, two stators mounted in said frame, two rotors mounted on a common shaft and adapted to be rotated within said stators, means for creating a magnetic flux in said rotors and stators, an armature winding on each of said stators consisting of two groups of coils, and electrical connections for connecting a coil group of one stator in series with a group of the other stator and for connecting the four groups in series witha center tap whereby voltage generated in one armature winding is added to the voltage generated in the other armature winding to produce one o! the said 180 phase related voltages.

2. Means for generating two voltages having a 180 phase relation comprising two alternators arranged in phase displaced relation each alternator having a rotor element and a stator element, separate means for creating a magnetic flux in each alternator, an armature winding on each of said stators consisting of two groups of coils, and electrical connections for connecting a coil group of one stator in series with a group of the other stator and for connecting the four groups in series with a common output connection whereby voltage generated in one armature winding is added to the voltage generated in the other armature winding to produce one of the said 180 phase related voltages.

3. An alternator for generating two voltages having a 180 phase relation in accordance with claim 1 characterized by the fact that the num ber of poles on one or the stators is equal to the number of poles on the other stator and that the number of poles on one of the rotors is equal to the number of poles on the other rotor.

4. Means for generating two voltages having a 180 phase relation in accordance with claim 2 characterized by the fact that the number of poles on the stator and rotor of onealternator is I equal to the number of poles on the stator and rotor of the other alternator, and means for synchronously rotating said rotors.

5. Means for generating two voltages having a 180 phase relation in accordance with claim 2 characterized in that the frequency generated by one rotor and stator element is equal to the frequency generated by the other rotor and stator element.

6. An alternator for generating two voltages having a 180 phase relation in accordance with claim 1 characterized by the, fact the two voltages are generated by fiux changes in a magnetic circuit which is common to the two rotors and the two stators.

'7. An alternator for generating two voltages having a'180 phase relation in accordance with claim 1 characterized by the fact that the magnetic polarity of one rotor is opposite to the magnetic polarity of the second rotor.

8. An alternator for generating two equal phase related voltages comprising means for generating a first and second voltage having other than a 180 phase relationfrneans for dividing each of said voltages into a plurality of voltages, means for combining a portion of said divided mature winding on each of said stators and sub divided into multiple groups, and series electrical produce one of the said 180 10 ages.

FLOYD WILLIAM IDEN. 

